Hydrogen can be used in internal combustion engines or more favourably in proton-exchange-membrane fuel cells to generate power so that the exhaust emission is simply water vapour. Recent studies have suggested that, regardless of the source of hydrogen, a complete switch to hydrogen fuel-cell vehicles in the transportation sector would likely lead to a significant improvement in health, air quality and climate. The benefits were derived from a complete elimination of common vehicle exhaust emissions.
The study, however, did not address the effect of greenhouse gases when hydrogen was derived from fossil fuels. It is widely recognized that the conventional methods of producing hydrogen from fossil fuels invariably produce carbon dioxide (natural gas steam reforming and coal gasification) and that in the long term hydrogen has to be produced by renewable sources such as solar energy and biomass. In the short- and mid-term future when hydrogen will be derived from fossil fuels, geosequestration of carbon dioxide is technically possible but is complicated by uncertain long-term environmental ramifications.
The route from fossil fuels to hydrogen does not necessarily involve the unavoidable production of carbon oxides (COx) which fundamentally challenges the raison d'être of the hydrogen economy.
Natural gas can be solid catalytically cracked into both hydrogen gas and solid carbon according to Equation (1).CH4→C+2H2  (1)
ΔHcracking,298K=74.81 kJ/mol, ΔGcracking,298K=50.72 kJ/mol
However, in practice two problems prevent catalytic conversion of methane to hydrogen from being practically viable.
Firstly, the conversion efficiencies are low and the carbon generated during catalytic conversion of methane quickly deactivates the catalyst and caulks up the cracking reactor. The lifetime of the catalyst is very short, typically of the order of a few hours. It is well established that the higher the conversion efficiency of the system, the quicker the catalyst is depleted.
Secondly, the carbon generated is known to be essentially amorphous when activated carbon is used as the catalyst. The amount of amorphous carbon which would be generated would be approximately 75% of the mass of methane undergoing catalytic conversion. A huge stockpile of amorphous carbon is potentially unstable and provides disposal and management considerations.
By a judicious use of selected catalysts, it is possible to produce a spectrum of carbon quarries, such as carbon fibres and carbon nanotubes. It is possible to obtain graphitized carbon as the carbon by-product, which has an established market and is known to be very stable, but the catalyst life span is known to be short.
There is a significant need for new and improved processes for catalytic conversion of methane, and other light hydrocarbons, to hydrogen and a carbon by-product which is stable and commercially valuable.
The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia as at the priority date of the application.